What are you using for your DAW?
I find it a much better workflow to add OZONE to my MASTER BUS - after which I have another BUS called "MASTER FADER" where I can do fades without affecting how the signal hits the compressors, limiters etc. before the mix hits the OUTPUTS
This also allows me to add a reference track outputting directly to the MASTER FADER so it bypasses all mastering effects that I am using on my MASTER BUS
I can then export directly out of my DAW in any format I want (CD, WAV, FLAC etc.)
I think PCs are powerful enough these days to handle the mixing and mastering within one project
I rarely output a stereo WAV file to then re-load into a "Mastering" environment
I find it much better to merge my mixing & mastering in one project
If during the mastering phase I discover something I want to change in the mix I simply tweak the mix at the same time as mastering
The "digital age" means we are able to think in different ways and lines between "tracking", producing, mixing and mastering are definitely getting blurred and even though I approach each area with a different mindset I am seeing the process more "as one"